The notification is to alert the user that's they are in private browsing mode - History, cookies not saved.

Hello shadow_rps, '''if you get the notification when you open a new tab and you are already in private browsing mode, then it is not normal''', check it in [https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode#os=win7&browser=fx17 Safe Mode], in [https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode#w_safe-mode-window_2 Safe Mode window] select '''''"Start in Safe Mode"''''' and see if this happen again, '''''if not''''' then see: [https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems#os=win7&browser=fx17 Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems] (If the problem does not happen in Safe Mode, it is most likely because of an extension, theme or hardware acceleration). thank you

This happens when the new tab page is set to about:newtab.<br /> You can set the browser.newtab.url pref to about: blank to prevent this. See this article about the New Tab page (about:newtab): *https://support.mozilla.org/kb/new-tab-page-show-hide-and-customize-top-sites